Savio L-Y. Woo

Savio L-Y. Woo
University of Pittsburgh | Pitt · Bioengineering

Ph.D., D.Sc. (Hon.), D.Eng.(Hon.)

About

554
Publications
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42,148
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Publications

Publications (554)
Conference Paper
The goal of ACL reconstruction surgery is to restore normal ligament function and knee kinematics. Multiple factors can contribute to its outcome. Studies using cadaveric knees have been conducted to examine the effect of surgical variables on ACL reconstruction (1–3,7). However, large inter-specimen variability, less-than-reproducible surgical tec...
Chapter
Composed of tibiofemoral and patellofemoral joints, the knee is a complex synovial joint in the human body, both in terms of anatomy and biomechanics. Common knee injuries include torn ligaments and tendons as well as menisci that could lead to cartilage degeneration and osteoarthritis. Therefore, a thorough understanding of the anatomy and biomech...
Book
This book provides state-of-the-art and up-to-date discussions on the pathology-related considerations and implications in the field of orthopaedic biomechanics. It presents fundamental engineering and mechanical theories concerning the biomechanics of orthopaedic and anatomical structures, and explores the biological and mechanical features that i...
Article
Full-text available
Background/objective: In anterior cruciate ligament reconstruction, a tendon graft, anchored by interference screws (IFSs), is frequently used as a replacement for the damaged ligament. Generally, IFSs are classified as being either metallic or polymeric. Metallic screws have sharp threads that lacerate the graft, preventing solid fixation. These...
Article
Background: Recently, a ring device was used for mechanical augmentation to aid the healing of ACL. In-vivo study using goat showed improved joint stability after ring repair in comparison to using biological augmentation alone. Objective of this study was to quantify the load and stress levels in the ACL and its femoral insertion site following r...
Chapter
The anterior cruciate ligament (ACL) is the most frequently injured ligament of the knee. Its surgical management has been using a soft tissue graft as a replacement. The results of ACL reconstruction have been successful for many patients as it can restore joint stability and relieve pain. However, longer term follow up studies have shown unsatisf...
Article
The International Symposium on Ligaments and Tendons (ISL&T) was inaugurated in 2000 in Orlando, Florida, USA. The primary purpose of the ISL&T was to call attention to the importance of ligament and tendon (L&T) research and to bring together bioengineers, biologists, and clinician-scientists in a forum where the most current research findings cou...
Article
A bioresorbable, mono-crystalline magnesium (Mg) ring device and suture implantation technique were designed to connect the ends of a transected anterior cruciate ligament (ACL) to restabilize the knee and load the ACL to prevent disuse atrophy of its insertion sites and facilitate its healing. To test its application, cadaveric goat stifle joints...
Article
The Classic revisits a landmark paper by Clancy and colleagues 'Anterior and posterior cruciate ligament reconstruction in rhesus monkeys—a histological, microangiographic and biomechanical analysis', published in 1981 in the Journal of Bone and Joint Surgery . At that time, this publication offered new and clinically relevant information on the fa...
Article
Full-text available
Recently, healing of a ruptured anterior cruciate ligament (ACL) is reconsidered. In a previous study, we have shown that the transected ACL can heal after treatment with the triple X locking suture alone or combined with small intestine submucosa (SIS). The first research question of this study was whether the healing ACLs in both groups show hist...
Article
Full-text available
Background/Objective We have previously shown that an extracellular matrix (ECM) bioscaffold derived from porcine small intestine submucosa (SIS) enhanced the healing of a gap injury of the medial collateral ligament as well as the central third defect of the patellar tendon. With the addition of a hydrogel form of SIS, we found that a transected g...
Chapter
Recent technological advancements have enabled researchers to accurately measure in vivo 3-dimensional (3-D) joint kinematics, as well as to determine the corresponding forces experienced by the individual soft tissues in and around the joint. In this chapter, the development of these new approaches will be reviewed, as well as how they could be co...
Article
Background Recently, many surgeons have chosen the quadriceps tendon (QT) as an autograft for anterior cruciate ligament (ACL) reconstruction. However, there have not been biomechanical studies that quantitatively evaluated knee function after reconstruction using a QT autograft. Purpose To measure the 6 degrees of freedom knee kinematics and in s...
Article
The insertions of ligaments and tendons to bone are morphologically and biomechanically complex. Within a short distance, the insertion (enthesis) is transformed from soft connective tissue to hard bone. In this chapter, we discuss the anatomy of the enthesis, including a review of the gross morphology as well as histology and appearance of two dis...
Article
Primary suture repair of the ACL has been used clinically in an attempt to heal the ruptured ACL. The results, however were not satisfactory which in retrospect can be attributed to the used suturing technique and the suboptimal healing conditions. These constraining conditions can be improved by introducing a new suturing technique and by using sm...
Article
The goal of this study was to determine the effects of peak knee valgus angle and peak knee abductor moment on the anterior, medial, and lateral tibial translations (ATT, MTT, LTT) in the "at risk" female knee during drop landing. Fifteen female subjects performed drop landings from 40 cm. Three-dimension knee motion was simultaneously recorded usi...
Article
For recurrent patellar dislocation, reconstruction of the medial patellofemoral ligament (MPFL) with replacement autografts has often been performed but with only little data on the tensile properties of the MPFL to guide graft selection. With its complex anatomy and geometry, these properties are difficult to obtain. In this study, we showed how t...
Chapter
In this chapter, the use of a robotic/universal force-moment sensor (UFS) testing system to gain quantitative data on multiple degree of freedom kinematics of the knee simultaneously with the in situ forces in normal and repaired soft tissues, is discussed. In particular, the complex interactions of the anteromedial and posterolateral bundles of th...
Article
The transverse carpal ligament is the volar roof of the carpal tunnel. Gross observation shows that the ligament appears to have fibers that roughly orient in the transverse direction. A closer anatomical examination shows that the ligament also has oblique fibers. Knowledge of the fiber orientation of the transverse carpal ligament is valuable for...
Chapter
By the year 2020, it is anticipated that telemedicine will become widely available so that special medical and surgical expertise can be made available worldwide. Also, novel imaging technologies will further increase our diagnostic capabilities dramatically. These and other new technologies will no doubt enhance the diagnostic aspect of medicine....
Article
Full-text available
The anterior cruciate ligament (ACL) has been well defined as the main passive restraint to anterior tibial translation (ATT) in the knee and plays an important role in rotational stability. However, it is unknown how closely the ACL and other passive and active structures of the knee constrain translations and rotations across a set of functional...
Article
Biological augmentation to heal a torn anterior cruciate ligament (ACL) has gained significant interest. This study examined the potential advantages of using extracellular matrix (ECM) bioscaffolds from galactosyl-α(1,3)galactose deficient pigs to heal the transected ACL. In 16 skeletally mature goats, the ACL in the right hindlimb was transected...
Article
Research has linked knee extensor moment and knee shear force to the non-contact anterior cruciate ligament injury during the landing motion. However, how these biomechanical performance factors relate to knee translations in vivo is not known as knee translations cannot be obtained with traditional motion capture techniques. The purpose of this st...
Article
Full-text available
Soft tissue allografts, such as the bone-patellar tendon-bone (BPTB) graft, have been frequently used for anterior cruciate ligament (ACL) reconstruction. As allografts are subjected to freezing and thawing for multiple cycles, the objective of this study was to measure the changes of the biomechanical properties of the human BPTB allograft after 4...
Conference Paper
Forming the palmar roof of the carpal tunnel, the transverse carpal ligament (TCL) continues to be the surgical target for carpal tunnel release which aims to relieve the symptoms of patients with carpal tunnel syndrome. However, the surgical procedures may cause several biomechanical and anatomical problems for the carpal tunnel [1]. Therefore, an...
Conference Paper
A torn anterior cruciate ligament (ACL) of the knee has poor healing potential, and thus, surgical reconstruction using soft tissue autografts is needed to restore knee stability. Unfortunately, these procedures have a high incidence of donor site morbidity and the progression to osteoarthritis in the long-term 1. In recent years, biological stimul...
Conference Paper
Extracellular matrix (ECM) bioscaffolds derived from animal sources, such as porcine small intestine submucosa (SIS) and urinary bladder matrix (UBM), have a successful history for application in clinical and/or experimental settings [1]. In our research center, we have demonstrated that the porcine SIS bioscaffolds could improve the morphological,...
Conference Paper
Patellar dislocation has an incidence of 5.8 per 100,000 per year in the US, and this number increases by five-fold for adolescents 1. Conservative management has been the preferred treatment, but recent follow-up studies have revealed a high redislocation rate. Similar outcomes were also found following primary repair of the medial patellofemoral...
Article
Full-text available
Previous laboratory studies of landing have defined landing techniques in terms of soft or stiff landings according to the degree of maximal knee flexion angle attained during the landing phase and the relative magnitude of the ground-reaction force. Current anterior cruciate ligament injury prevention programs are instructing athletes to land soft...
Article
Extracellular matrix (ECM) bioscaffolds, such as porcine small intestine submucosa (SIS) and urinary bladder matrix (UBM), have been successfully used to improve soft tissue healing. Yet they contain plenty of galactose α1,3 galactose (αGal) epitopes, which cause rejection responses in pig organ transplantation to human. Recently, ECM bioscaffolds...
Article
Full-text available
Background Lower extremity alignment (LEA) measures have been linked to non-contact anterior cruciate ligament (ACL) injuries. High deceleration movements have been implicated in non-contact ACL injury mechanisms; and, evidence suggests that greater anterior tibial translation (ATT) may occur in healthy knees that demonstrate greater laxity compare...
Article
Full-text available
Background When assessing non-contact anterior cruciate ligament (ACL) injury risk, prospective measures of high valgus knee angle (>8°) and high knee abduction moment (>25 Nm) measured during landings have been shown to predict ACL injury in female athletes. Objective The purpose of this study was to determine the relationships between these 'high...
Article
Functional tissue engineering (FTE) approaches have shown promise in healing an injured anterior cruciate ligament (ACL) of the knee. Nevertheless, additional mechanical augmentation is needed to maintain joint stability and appropriate loading of the joint while the ACL heals. The objective of this study was to quantitatively evaluate how mechanic...
Article
The six degrees of freedom knee motion during dynamic activities is not well understood. Biplane fluoroscopy was used to measure the three-dimensional rotations and translations of healthy knees during stiff drop landings and to determine the relationships between three-dimensional rotations and anterior (ATT) and lateral tibial translations (LTT)....
Article
Full-text available
Passive anterior knee laxity has been linked to non-contact ACL injury risk. High deceleration movements have been implicated in the non-contact ACL injury mechanism, and evidence suggests that greater anterior tibial translations (ATT) may occur in healthy knees that are lax compared to a tight knee. The purpose of this study was to determine the...
Article
Use of novel tissue engineering approaches to heal an injured anterior cruciate ligament (ACL) requires suture repair and/or augmentation to provide joint stability. We evaluated the effects of the location of suture augmentation at the femur and tibia in terms of joint stability using a goat model. Eight goat stifle joints were tested with augment...
Conference Paper
Due to the poor healing potential of the anterior cruciate ligament (ACL) of the knee, surgical reconstruction using soft tissue replacement grafts is performed to restore knee stability and function. However, the surgery has serious complications including a high incidence of donor site morbidity and the development of osteoarthritis in the long-t...
Article
Full-text available
Ligaments and tendons are dense connective tissues that are important in transmitting forces and facilitate joint articulation in the musculoskeletal system. Their injury frequency is high especially for those that are functional important, like the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) of the knee as well as the gle...
Article
The practice of orthopaedic sports medicine, specifically the management of ligament and tendon injuries, will experience dramatic changes in the near future. Rapid technological advancements, especially in imaging, will greatly increase the speed and accuracy of diagnosing musculoskeletal injuries. On the contrary, effective treatment strategies w...
Article
Harvesting both the semitendinosus and gracilis tendons for anterior cruciate ligament (ACL) reconstruction has a negative impact on muscle strength as well as knee function and stability. With a new "All-inside" technique, using only one hamstrings tendon (semitendinosus or gracilis) is possible because of a reduction in length requirements. The r...
Article
The two functional bundles of the anterior cruciate ligament (ACL), namely, the anteromedial (AM) and posterolateral (PL) bundles, must work in concert to control displacement of the tibia relative to the femur for complex motions. Thus, the replacement graft(s) for a torn ACL should possess similar tension patterns. The objective of the study was...
Conference Paper
The anterior cruciate ligament (ACL) of the knee is frequently injured, but it has limited healing potential. Surgical reconstruction using soft tissue autografts is often required for active patients. However, about 20–25% of patients have less than satisfactory results and some even developed of osteoarthritis in the long-term. Thus, there is a n...
Article
Full-text available
Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and decelerat...
Article
In our research center, we have developed and utilized a novel robotic/universal force-moment sensor testing system to gain quantitative data on multiple-degree-of-freedom kinematics of the knee simultaneously with data on the in situ forces in normal and repaired soft tissues. In particular, we have investigated the complex interaction of the ante...
Article
Mechanical devices, such as robotic manipulators have been designed to measure joint and ligament function because of their ability to position a diarthrodial joint in six degrees-of-freedom with fidelity. However, the precision and performance of these testing devices vary. Therefore, the objective of this study was to determine the effect of syst...
Article
Ligaments and tendons serve a variety of important functions in maintaining the structure of the human body. Although abundant literature exists describing experimental investigations of these tissues, mathematical modeling of ligaments and tendons also contributes significantly to understanding their behavior. This paper presents a survey of devel...
Article
Previous studies have shown that cultured cells align with the local topography of their substrate following a concept called "contact guidance." Additionally, if the topography is highly aligned, the cells produce newly synthesized matrix that is also aligned. The objective of this study was to elucidate the positive effect of cell seeding on an e...
Article
Full-text available
The porcine small intestine submucosa, an extracellular matrix-derived bioscaffold (ECM-SIS), has been successfully used to enhance the healing of ligaments and tendons. Since the collagen fibers of ECM-SIS have an orientation of +/- 30 degrees , its application in improving the healing of the parallel-fibered ligament and tendon may not be optimal...
Article
Trauma to the knee joint often results in injury to one or more supporting soft tissue structures, such as the medial collateral (MCL) and anterior cruciate (ACL) ligaments. Also, a portion of the patellar tendon (PT) is frequently used as a replacement graft for the ACL, resulting in a PT defect. The healing responses of these tissues are dramatic...
Article
Bioscaffolds have been successfully used to improve the healing of ligaments and tendons. In a rabbit model, the application of porcine small intestine submucosa (SIS) to the healing medial collateral ligament (MCL) resulted in improved mechanical properties with the formation of larger collagen fibrils. Thus, the objective of the study was to find...
Article
The contribution of biomechanics to the advancement of management of ligament and tendon injuries has been significant. Thanks to Professor Y.C. Fung's writing and guidance, our field of research has done fundamental work on anatomy and biology of ligaments and tendons, developed methods to accurately determine mechanical properties, identified var...
Article
The anterior cruciate ligament (ACL) is commonly injured. The stress distribution in the ACL is the key for understanding its function and injury mechanism, as well as for developing optimal surgical reconstruction protocols. In this study, a three-dimensional subject-specific finite element model of human ACL was developed. Bony geometries were re...
Article
The anterior cruciate ligament (ACL) has irregular geometry and spirally oriented fiber bundle organization, which are closely related to its physiological function. In previous finite element (FE) models, however, these two features are neglected due to the difficulty of obtaining its complex geometry and spiral fiber bundle orientation. Based on...
Article
Following harvest of a bone-patellar tendon-bone (BPTB) autograft, the central third of the patellar tendon (PT) does not heal well. The healing tissues also form adhesions to the fat pad and can cause abnormal patellofemoral joint motion. The hypotheses were that a bioscaffold could enhance patellar tendon healing through contact guidance and chem...
Chapter
Classical referenceBiochemical composition of muscle extracellular matrix: the effect of loadingTendon injuryBiomechanics of human skeletal muscle-tendon flexibilityLigaments: physiology and repairSummaryMultiple choice questions
Conference Paper
Ligaments and tendons of the knee are subjected to large loads during sports and work related activities, and thus, are frequently injured. For the anterior cruciate ligament (ACL) and medial collateral ligament (MCL), there are over 100,000 and 50,000 annual tears, respectively, in the United States alone. As a torn ACL has limited healing potenti...
Chapter
Classical referenceIntroduction: knee problems in sportsAnatomy and biomechanicsHistory and physical examinationImaging of the kneeFractures and chondral injuriesMeniscal injuriesLigament injuriesOveruse injuriesThe patellofemoral jointRehabilitation of knee injuriesSummaryMultiple choice questions
Article
Previous studies have shown that increasing tibial slope can shift the resting position of the tibia anteriorly. As a result, sagittal osteotomies that alter slope have recently been proposed for treatment of posterior cruciate ligament (PCL) injuries. Increasing tibial slope with an osteotomy shifts the resting position anteriorly in a PCL-deficie...
Article
For anterior cruciate ligament reconstruction with a double-bundle procedure, one of the major concerns is to not predispose either one of the grafts to risk of failure by overloading. Knee flexion angles between 15 degrees and 45 degrees for anteromedial graft fixation and 15 degrees for posterolateral graft fixation are safe for both grafts in do...
Article
Full-text available
Extracellular matrix scaffolds derived from porcine small intestinal submucosa (SIS-ECM) have been shown to promote the formation of site-specific tissue in a number of preclinical animal studies. However, this constructive remodeling process requires that the scaffold be subjected to a site-specific mechanical environment. The specific quantitativ...
Conference Paper
Central third bone-patellar tendon-bone (BPTB) autografts are commonly used for anterior cruciate ligament (ACL) reconstructions. Following surgery, complications arise at the donor site, including extension deficits and anterior knee pain [1]. These complications are partially caused by inadequate healing of the patellar tendon (PT) as well as adh...
Conference Paper
Robotic technology has been adopted for studying the biomechanics of the knee joint by our research center and others since 1993 to gain a fundamental understanding of the knee, as well as to provide orthopedic surgeons with scientific data on the efficacy of various reconstructive techniques [1–4]. A robotic testing system generally consists of a...
Article
When performing a stress-relaxation test of soft tissues, a small preload is usually applied to the specimen to remove slack and provide a gauge length. This preload is generally assumed to be negligible. However, for tissues with a low stiffness, such as healing ligaments and tendons, the preload, which corresponds to a prestress, may be a signifi...
Article
Full-text available
The article summarizes the collective views expressed at the fourth session of the workshop Tissue Engineering--the Next Generation, which was devoted to the translation of results of tissue engineering research into applications. Ernst Hunziker described the paradigm of a dual translational approach, and argued that tissue engineering should be gu...
Article
Full-text available
Improving our understanding of the design requirements of biologically derived collagenous scaffolds is necessary for their effective use in tissue reconstruction. In the present study, the collagen fiber kinematics of small intestinal submucosa (SIS) was quantified using small angle light scattering (SALS) while the specimen was subjected to presc...
Article
Biomechanical testing protocols for ligaments can be extensive and span two or more days. During this time, a specimen may have to undergo more than one cycle of freezing and thawing. Thus, the objective of this study was to evaluate the effects of refreezing on the viscoelastic and tensile properties of ligaments. The femur-medial collateral ligam...
Article
In situ force in the anterior cruciate ligament (ACL) has been quantified both in vitro in response to relatively simple loads by means of robotic technology, as well as in vivo in response to more complex loads by means of force transducers and computational models. However, a methodology has been suggested to indirectly estimate the in situ force...
Article
Full-text available
Fiber network theory was developed to describe cloth, a thin material with strength in the fiber directions. The interosseous ligament (IOL) of the forearm is a broad, thin ligament with highly aligned fibers. The objectives of this study were to develop a model of the stress and strain distributions in the IOL, based on fiber network theory, to co...
Article
Full-text available
Although anatomical double-bundle anterior cruciate ligament reconstruction can successfully restore normal knee biomechanics for knees with typical varus-valgus alignment, the efficacy of the same reconstruction method for knees after a valgus high tibial osteotomy is unclear. Anatomical double-bundle anterior cruciate ligament reconstruction for...